Question

Scientist calculated the net primary productivity (NPP) at two different forest sites. Both forests have the same gross primary productivity (GPP). Forest A has a net primary productivity of 1650 kcal/m^2/year, and forest B has a net primary productivity of 1110 kcal/m^2/year. Which one of the following statements is best supported by the data?

A) Forest A has a higher GPP than forest B
B) Forest B has a higher GPP than forest A
C) Forest A is more productive in converting sunlight to biomass
D) Forest B is more productive in converting sunlight to biomass

Answer 1

Forest A, with a higher net primary productivity than Forest B while having the same gross primary productivity, is more productive in converting available energy to biomass after accounting for respiration.

Step-by-step explanation:

In comparing the net primary productivity (NPP) of two different forest sites that have the same gross primary productivity (GPP), we see that Forest A has an NPP of 1650 kcal/m2/year and Forest B has an NPP of 1110 kcal/m2/year. The NPP is the energy that remains in the primary producers after accounting for the organisms' respiration and metabolic heat loss. Since both forests have the same GPP, the difference in their NPP means that Forest A has lower respiration rates compared to Forest B, thus retaining more energy as biomass. Therefore, it is not that Forest A has a higher GPP or Forest B is more efficient at converting sunlight to biomass, but rather that Forest A is more productive in terms of its efficiency in using the available energy to create biomass after subtracting the energy used in respiration.